Hedgehog signaling has a protective effect in glucocorticoid-induced mouse neonatal brain injury through an 11βHSD2-dependent mechanism
Vivi M. Heine, David H. Rowitch
Vivi M. Heine, David H. Rowitch
Published January 26, 2009
Citation Information: J Clin Invest. 2009;119(2):267-277. https://doi.org/10.1172/JCI36376.
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Research Article

Hedgehog signaling has a protective effect in glucocorticoid-induced mouse neonatal brain injury through an 11βHSD2-dependent mechanism

Abstract

Glucocorticoids (GCs) are administered to human fetuses at risk of premature delivery and to infants with life-threatening respiratory and cardiac conditions. However, there are ongoing concerns about adverse effects of GC treatment on the developing human brain, although the precise molecular mechanisms underlying GC-induced brain injury are unclear. Here, we identified what we believe to be novel cross-antagonistic interactions of Sonic hedgehog (Shh) and GC signaling in proliferating mouse cerebellar granule neuron precursors (CGNPs). Chronic GC treatment (from P0 through P7) in mouse pups inhibited Shh-induced proliferation and upregulation of expression of N-myc, Gli1, and D-type cyclin protein in CGNPs. Conversely, acute GC treatment (on P7 only) caused transient apoptosis. Shh signaling antagonized these effects of GCs, in part by induction of 11β-hydroxysteroid dehydrogenase type 2 (11βHSD2). Importantly, 11βHSD2 antagonized the effects of the GCs corticosterone, hydrocortisone, and prednisolone, but not the synthetic GC dexamethasone. Our findings indicate that Shh signaling is protective in the setting of GC-induced mouse neonatal brain injury. Furthermore, they led us to propose that 11βHSD2-sensitive GCs (e.g., hydrocortisone) should be used in preference to dexamethasone in neonatal human infants because of the potential for reduced neurotoxicity.

Authors

Vivi M. Heine, David H. Rowitch

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Figure 2

Dex treatment inhibits neonatal granule cell precursor proliferation.

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Dex treatment inhibits neonatal granule cell precursor proliferation. (A...
(A–H) P7 mouse pups were treated with vehicle (Veh; A–D) or Dex (E–H). (A and E) Chronic Dex treatment disrupted cerebellar foliation in lobes II–VII (arrows). Original magnification, ×20. The boxed region in A is shown at higher magnification in B, C, F, and G. (B and F) Immunocytochemistry for Zic1 and pH3 (arrows). (C and G) Immunocytochemistry for Casp3 (arrows). Dex did not change the mean total number of Calbindin-positive Purkinje cells (not shown). PL, Purkinje cell layer. The boxed region in C is shown at higher magnification in D and H. (D and H) TUNEL assay. Dotted lines denote the outer border of the EGL. (I and J) Mean EGL surface area per section (I) and proportional to the IGL (J). (K) pH3+ cells per sagittal section of mice treated with vehicle, Dex, Pred, or Cort. (L) Number of apoptotic cells in the EGL. (M) Number of Casp3+ and pH3+ cells after acute treatment. Original magnification, ×1,000. (N) Casp3+ cells during chronic treatment, both total number and per mm2 EGL. (O) Dex treatment 2 h after CldU injection (see Figure 1) did not affect the number of CldU+ cells, but significantly decreased the number of CldU+ldU+ cells. Original magnification, ×1,000. (P) Western blot analysis of protein lysates of whole cerebella. Zic1 protein levels, shown as estimated mean ± SD number of cells per sagittal section, significantly increased after Dex treatment (P < 0.01). Scale bars: 100 mm. For each group, n is shown within the corresponding bar. Asterisks denote significant differences versus respective vehicle groups; exact P values are shown in Results.